ClickHouse/dbms/include/DB/DataStreams/MaterializingBlockOutputStream.h

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#pragma once
#include <DB/Columns/ColumnConst.h>
#include <DB/DataStreams/IBlockOutputStream.h>
#include <statdaemons/ext/range.hpp>
namespace DB
{
/** Преобразует столбцы-константы в полноценные столбцы ("материализует" их).
*/
class MaterializingBlockOutputStream : public IBlockOutputStream
{
public:
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MaterializingBlockOutputStream(const BlockOutputStreamPtr & output)
: output{output} {}
void write(const Block & original_block) override
{
/// copy block to get rid of const
auto block = original_block;
for (const auto i : ext::range(0, block.columns()))
{
ColumnPtr & col = block.getByPosition(i).column;
if (col->isConst())
col = dynamic_cast<IColumnConst &>(*col).convertToFullColumn();
}
output->write(block);
}
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void flush() override { output->flush(); }
void writePrefix() override { output->writePrefix(); }
void writeSuffix() override { output->writeSuffix(); }
private:
BlockOutputStreamPtr output;
};
}